It looks like you've uploaded a worksheet titled
"Worksheet: Dihybrid Crosses", which involves genetics problems related to
dihybrid crosses—crosses between two organisms that are heterozygous for two different traits.
Since I can't view images directly, I'll guide you through how to solve dihybrid cross problems step-by-step, based on the typical structure of such worksheets. If you can describe the specific problem or provide the text from the image (e.g., the traits, genotypes, or Punnett squares), I can give a more targeted explanation.
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🔬 What is a Dihybrid Cross?
A
dihybrid cross examines the inheritance of
two traits simultaneously. Each parent is
heterozygous for both traits (e.g., AaBb × AaBb).
For example:
- Trait 1: Seed color (Y = yellow, y = green)
- Trait 2: Seed shape (R = round, r = wrinkled)
Parental cross:
YyRr × YyRr
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✔ Step-by-Step Solution
#### Step 1: Determine the gametes
Each parent produces gametes with one allele for each gene.
For
YyRr, possible gametes are:
- YR
- Yr
- yR
- yr
So, there are
4 types of gametes.
#### Step 2: Set up a 4×4 Punnett square
Label the rows and columns with the gametes.
| | YR | Yr | yR | yr |
|-------|--------|--------|--------|--------|
|
YR| | | | |
|
Yr| | | | |
|
yR| | | | |
|
yr| | | | |
#### Step 3: Fill in the squares
Combine alleles from each row and column.
Example:
- YR + YR → YYRR
- YR + Yr → YYRr
- etc.
#### Step 4: Analyze the offspring
Count the phenotypes and genotypes.
For
YyRr × YyRr, the expected phenotypic ratio is:
>
9:3:3:1
- 9 Yellow, Round
- 3 Yellow, Wrinkled
- 3 Green, Round
- 1 Green, Wrinkled
This is the classic dihybrid cross ratio.
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🧩 Common Problems on These WorkSheets
1.
Fill in the Punnett square given parental genotypes.
2.
Determine the phenotypic ratio of offspring.
3.
Calculate probabilities (e.g., "What is the chance of a green, wrinkled seed?").
4.
Use real-world examples (like pea plants, fruit flies, etc.).
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📝 Example Problem (Typical):
> In pea plants, yellow seeds (Y) are dominant over green (y), and round seeds (R) are dominant over wrinkled (r). Cross two heterozygous plants (YyRr × YyRr). What are the possible offspring phenotypes and their ratios?
Answer:
- Phenotypic ratio:
9 Yellow Round : 3 Yellow Wrinkled : 3 Green Round : 1 Green Wrinkled
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If you can tell me:
- The specific traits involved,
- The parental genotypes,
- Or what part of the worksheet you're stuck on,
I can help you
fill in the Punnett square,
calculate ratios, or
explain any specific question.
Just describe it, and I’ll walk you through it!
Parent Tip: Review the logic above to help your child master the concept of dihybrid crosses worksheet answers.
